1.Field of the Invention
The present invention relate to pneumatic radial tires having a belt layer and a reinforcing layer radially outwardly arranged around a toroidal carcass layer.
2. Background of the Invention
As conventional pneumatic radial tires, for example, a tire disclosed in Japanese patent application Laid-open No. 1-25,636 is known. This pneumatic radial tire includes a toroidal carcass layer in which a number of cords are radially extended and buried. A belt layer is arranged radially outwardly around the carcass layer and a number of substantially inextensible cords are buried inclinedly with respect to the tire equatorial plane. A reinforcing layer is arranged between the carcass layer and the belt layer, and a number of waved reinforcing elements extend in parallel to a tire equatorial plane as a whole and are buried at the same phase in the reinforcing layer to prevent separation of belt layer.
However, since the tread portion of such a conventional pneumatic radial tire increases its diameter through radially outward growth thereof on inflation with an internal pressure or during running at high speeds, each reinforcing element is stretched in a longitudinal direction (circumferential direction) to decrease its amplitude. Such deformation of each of the reinforcing elements produces meridian forces reversing every half wavelength for each reinforcing element. Since the phase is identical for all the reinforcing elements as mentioned above, great forces are produced through integration of the meridian forces to influence the surrounding carcass. As a result, portions of the carcass layer spaced in the circumferential direction displace alternatively in radially opposite directions, so that circumferentially spaced numerous waves (uneven portions) are formed in the carcass layer. When the carcass layer is waved in this manner, this influences the outer surface of the sidewall portion, so that the sidewall portion is also circumferentially waved to extremely deteriorate the appearance of the tire.